How to handle random factors in rma.mc (metafor)?

I have a question regarding the use of rma.mv (metafor) in a multivariate meta-analysis, in particular how to handle random factors. I have outcomes that vary not only between trials but also between subjects. In other words, there are outcomes that have been measured twice in one subject using different methods (mRNA, protein). This is true for only a few studies, while others only report one method.

So far, I have 'trial' as a random variable. If I add 'subject' as another random variable, I receive an error message in larger datasets saying that the optimizer could not converge. What would you suggest?

Please find attached the code and a test dataset. Thank you very much in advance. Lisa

yi <- dat1$SMD
V <- dat1$Variance
W<-dat1$NoPatients
res <- rma.mv(yi, V, W,mods = ~ Gen - 1, random =~ Gen | trial,struct="UN", data=dat1)
res

Multivariate Meta-Analysis Model (k = 53; method: REML)

Variance Components: 

outer factor: trial (nlvls = 11)
inner factor: Gen   (nlvls = 4)

estim    sqrt  k.lvl  fixed   level
tau^2.1    0.2331  0.4828      5     no  NDUFA1
tau^2.2    0.0009  0.0303     10     no  NDUFS1
tau^2.3    0.0147  0.1212     17     no  NDUFV1
tau^2.4    0.0595  0.2440     21     no  NDUFV2

    rho.NDUFA  rho.NDUFS  rho.NDUFV1  rho.NDUFV2    NDUFA  NDUFS  NDUFV1  NDUFV2
NDUFA1          1     0.5679      0.9493      0.9989        -     no          no      no
NDUFS1     0.5679          1      0.2804      0.6060        1      -      no      no
NDUFV1     0.9493     0.2804           1      0.9335        1      4       -      no
NDUFV2     0.9989     0.6060      0.9335           1        2      4       5       -

Test for Residual Heterogeneity: 
QE(df = 49) = 119.9290, p-val < .0001

Test of Moderators (coefficient(s) 1:4): 
QM(df = 4) = 11.8456, p-val = 0.0185

Model Results:

estimate      se     zval    pval    ci.lb    ci.ub    
GenNDUFA1    0.4482  0.3377   1.3272  0.1845  -0.2137   1.1100    
GenNDUFS1   -0.1999  0.0641  -3.1211  0.0018  -0.3255  -0.0744  **
GenNDUFV1    0.0145  0.0779   0.1857  0.8527  -0.1382   0.1671    
GenNDUFV2   -0.0109  0.1272  -0.0854  0.9319  -0.2601   0.2383    

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Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1